From the Manual

- Squelch:
With the squelch setting you can suppress weak transponder signals. This is sometimes useful if participants are walking near the loop or the coaxial cable and are picked up accidently. E.g. if the squelch setting is set to 60, all transponders with received strength below 60 will be ignored.

Meaning the weaker signals of transponders further away from the loop will be ignored. I have found the RC3/4 decoder is way more sensitive than the RC2. So you may have to re-think your loop location. You need a minimum of 3 or 4 feet from adjoining lanes...... you may have cars in other lanes picking up under the minimum lap time.